Multiple stellar populations in Globular Clusters: collection of information from the Horizontal Branch

The majority of the inhomogeneities in the chemical composition of Globular Cluster (GC) stars appear due to primordial enrichment by hot-CNO cycled material processed in stars belonging to a first stellar generation. Either massive AGB envelopes subject to hot bottom burning, or the envelopes of massive fastly rotating stars could be the progenitors. In both cases, the stars showing chemical anomalies must have also enhanced helium abundance, and we have proposed that this higher helium could be at the basis of the many different morphologies of GC horizontal branches (HB) for similar ages and metallicities. The helium variations have been beautifully confirmed by the splitting of the main sequence in the clusters omega Cen and NGC 2808, but this effect can show up only for somewhat extreme helium abundances. Therefore it is important to go on using the HB morphology to infer the number ratio of the first to the second generation in as many clusters as possible. We exemplify how it is possible to infer the presence of a He-rich stellar component in different clusters thanks to different HB features (gaps, RR Lyr periods and period distribution, ratio of blue to red stars, blue tails). In many clusters at least 50% of the stars belong to the second stellar generation, and in some cases we suspect that the stars might all belong to the second generation. We shortly examine the problem of the initial mass function required to achieve the observed number ratios and conclude that: 1) the initial cluster must have been much more massive than today's cluster, and 2) formation of the second stellar generation mainly in the central regions of the cluster may help in obtaining the desired values.Comment: to appear in the Proceedings of IAU Symposium 246 ``Dynamical Evolution of Dense Stellar Systems", E. Vesperini, M. Gierzs & A. Sills, eds., Cambridge University Pres

Termologia del lago di Bracciano: onde interne

In precedenti lavori, sono stati 1101'ta.t.i alcuni cont.ributi ) alla conoseenza·dei moti liberi e forzati del lago (li Bmceiano,lll'eso nel suo insipnlP, eonsitlemto cioè comebaeino oSf'illant.e nella SWl interezza

Consuming pottery at early Prepalatial Sissi. Preliminary observations on the EM IIA and B ceramic deposits from the settlement

During the recent 2015-2019 excavation campaigns, the Kephali hill at Sissi yielded a number of Prepalatial deposits that can be attributed to the EM II period (ca. 2700/2650–2200 BCE), offering, for the moment, the earliest evidence for occupation of the settlement in the Bronze Age. The most important architectural remains dating to EM II were found in 2019, immediately to the west of the Neopalatial Court-Centred Building (CCB), on a higher terrace that is called the Upper Terrace Extension (UTE). Since neither their excavation nor their study is completed, we are not yet sure whether we are dealing with one or more separate structures. Moreover, in the West and North-West Wings of the CCB, EM IIA and EM IIB levels were identified. In this chapter, some of the pottery assemblages found in these different areas is presented. Observations are evidently preliminary since only part of the deposit could be studied

Mixing, Enhanced Helium and Blue Tails in Globular Clusters

We investigate the consequences of an increase in the envelope helium abundance of pre-helium flash red giants in globular clusters. Comparing predictions with the CM diagrams of a few crucial GC, one finds no evidence for a substantial increase in the surface helium content of HB members of these clusters, at least for objects in the RR Lyrae region or close to it. The possibility that the most peculiar giants belong to the asymptotic giant branch is discussed. The consequences of a delay in the helium flash are briefly examined

Ulteriori esperienze geofisiche sul lago di Caldouazzo. Morfologia ed origine delle sesse. Dati microtermologici. Progressivo insabbiamento elei piccoli lagbi*.

The limnographic, barographic and tliermological recordings,taken in a week of October of the years 1906, 1967 and 1971 onthe Lake of Caldonazzo, are reviewed. The properties of free uninodal,binodal etc. oscillations of the Lake have been examined, once again withthe result that they coincide with the values previously elaborated theoretically:the amplitudes of uninodals in the North (Lido di San Cristoforo)are about twice as large as those measured in the extreme South (Lido diCaldonazzo); the behaviour of uninodals in the Northern part of the Lake(besides the uninode) in conformity with the theory, etc.The simultaneous function of a microbarograph, mounted near theLido of San Cristoforo, proved that the main, if not exclusive, reason ofthe seiches lies in the interaction between the atmosphere and the hydrosphere.The passage of even the slightest pressure variations above theLake, with rhythms of 10m, 5m, . . . cause an immediate response of theLake by free uninodal, binodal. . . oscillations, and the amplitude of wateroscillations is all the larger the more the period of perturbing causes approachesthe period of the corresponding free oscillation, in other words,the more it approaches resonance.Observations on microvariations of temperature have been made aswell which may occur on very short periods (in the order of 1 -2 sec) andgive evidence of a swift brownian motion of liquid molecules. Thismust have a considerable influence on the Lake's microbiology. The increaseof the period of uninodals, against the period of batliymetric mea